August 19: Romy Connolly is lifted from a rescue boat by Pittsburgh emergency responders after being caught in a flash flood, in Pittsburgh.
(AP)

PITTSBURGH – The flash flooding that killed four people and forced others to swim to safety or climb onto car roofs was a freak accident caused by heavy rainfall that overwhelmed the sewer system just as rush-hour traffic clogged low-lying city streets, officials said Saturday.

A mother and her two daughters died in Friday's flood after becoming trapped in their vehicle and rising water pinned it to a tree. Another woman's body was washed into the Allegheny River, where she was found Saturday morning.

Back-to-back storms pounded the city with 3 to 4 inches of rain. The water drained rapidly onto Washington Boulevard, a main street near the Allegheny River on the city's east side, with a force too great for a pair of sewer pipes 9 feet in diameter. The torrent blew off 60-pound manhole covers,

"We had geysers here," said Raymond DeMichiei, deputy director of the city Office of Emergency Management.

"There's only so much any drainage system can handle," said Jim Struzzi, a spokesman for the Pennsylvania Department of Transportation. PennDOT maintains the roadway, but the city is responsible for the pipes underneath, part of aging sewer system.

The area's topography presents near-perfect conditions for flooding.

Hills line both sides of the section of Washington Boulevard that flooded and the boulevard itself slopes down as it stretches north toward the Allegheny River. When heavy rains hit, water rushes in from three directions.

The low-lying area was apparently once a creek bed and "the watershed is huge for this," DeMichiei said.

Flooding is not uncommon in the area, but this was "a little bit more spectacular than usual," he said.

Rescue crews used inflatable boats to reach drivers marooned by flood waters as deep as 9 feet, while others swam to safety on their own.

Rhodearland "Bob" Bailey of Penn Hills, who is about 80, was rescued from the roof of his car.

He said he heard a woman yelling for help but couldn't see anything because the water was coming down so fast, he told the Pittsburgh Tribune-Review.

"I've never seen nothing like this in my life," he said. "Lord have mercy."

Authorities identified the mother and children who died as Kimberly Griffith, 45, of Plum, and her daughters, Brenna, 12, and Mikaela, 8, Pittsburgh public safety director Michael Huss said at a Saturday news conference.

A woman who answered the phone at the family's home said relatives weren't ready to comment on the loss yet. The family lives in a neat brick home where a few cars were in the driveway Saturday afternoon but the middle-class neighborhood was mostly quiet.

The girls were students in the Plum Borough School District, which issued a statement of sympathy to the family Saturday. Grief counseling will be available for students Monday and Tuesday.

"In the days and weeks to come, we will remain attentive and responsive to the needs that emerge from this tragedy as we attempt to cope with this loss," the statement said.

The body of a 72-year-old woman who had been reported missing Friday was found in the river near the Highland Park Bridge on Saturday. The Allegheny County Medical Examiner's Office identified her as Mary Saflin of Oakmont.

In 1998, a thunderstorm accompanied by a tornado that struck Mount Washington touched off worse flooding in the area, though it did not result in deaths. The flooding covered a swath about two miles wide, making it appear that it was part of the river.

DeMichiei said emergency officials will discuss steps to avoid future tragedies from flooding at the site.

Educating people about the danger of being in a vehicle in a flash flood is key, he said. For example, the Federal Emergency Management Agency has distilled its advice in such situations to a slogan: "Turn around, don't drown."

"If water starts coming up the side of your car, get the hell out and get to higher ground," DeMichiei said.

Witnesses described Friday's scene as chaotic.

The water was so deep that rescuers in a boat intent on rescuing a man from a tree floated over the Griffiths' car without realizing it.

"The bottom of the boat didn't even scrape against the top of the car," DeMichiei said.

People were clinging to trees, poles and car roofs, KDKA-TV reported. One woman tried to scramble to the roof of her car but the water was moving so fast, she was dragged along in it,then grabbed on to a truck.

"You started to see -- even a red dump truck floating," Marion Marty of Sarver told the station. "I mean, I never saw anything like it before in my life!"

"We had cars fully covered and we didn't know they were there," DeMichiei said. One man appeared to be standing in waist-deep water, and it wasn't until crews reached him that they realized "he was standing on his SUV," he said.